The mechanism of coupling of electrochemical gradients of sodium to the transport of amino acids will be investigated from the standpoint of stoichiometry, gating potentials, and driving forces. A technique which has been successful in isolating the binding protein for aspartate will be applied to other amino acid transporters and an effort will be made to reconstitute these proteins into azolectin liposomes to restore transport function. Membrane vesicles have been prepared which contain active ATPase. This system will be used to evaluate the role of electrochemical ion gradients in ATPase function with particular emphasis on energy coupling. The role of halorhodopsin in generating electrochemical sodium gradients will be examined further and the relationship of halorhodopsin to bacteriorhodopsin and Na ion/H ion-antiporter function will be studied.